1. Field of the Invention
This invention relates to a liquid crystal display apparatus, and more particularly to a liquid crystal display apparatus wherein a photo-sensor element is provided in a pixel region of a liquid crystal panel and receives, at a light receiving face thereof, light incident thereto through a liquid crystal layer to produce received light data.
2. Description of the Related Art
A liquid crystal display apparatus includes, as a display panel, a liquid crystal panel wherein a liquid crystal layer is enclosed between a pair of substrates. The liquid crystal panel is formed, for example, as a transmission type liquid crystal panel which modulates and transmits therethrough illuminating light emitted from an illuminating apparatus such as a backlight provided on the rear face of the liquid crystal panel. An image is formed from the modulated illuminating light on the front face of the liquid crystal panel.
The liquid crystal panel is formed, for example, as an active matrix type liquid crystal panel which includes a TFT (thin film transistor) array substrate wherein a plurality of thin film transistors each functioning as a pixel switching element are formed in each pixel region. In the liquid crystal panel, an opposing substrate is disposed in an opposing relationship to the TFT array substrate, and a liquid crystal layer is provided between the TFT array substrate and the opposing substrate.
In the liquid crystal panel of the active matrix type, an electric field generated between a pixel electrode and a common electrode when each pixel switching element inputs a potential to the pixel electrode is applied to the liquid crystal layer to vary the orientation of liquid crystal molecules of the liquid crystal layer. As a result, the transmittance of light transmitted through the pixel is controlled to modulate the light transmitted through the pixel to carry out display of an image.
As regards such a liquid crystal panel as described above, such display modes as a TN (Twisted Nematic) mode, an ECB (Electrically Controlled Birefringence) mode and a vertical orientation mode are known. In addition, as modes wherein a transverse electric field is applied to the liquid crystal layer, various modes such as an IPS (In-Plane Switching) mode and an FFS (Fringe Field Switching) mode are known. Such modes as mentioned above are described, for example, in Japanese Patent Laid-Open No. 2007-226200.
Meanwhile, as such a liquid crystal panel as described above, a liquid crystal panel has been proposed which includes, in addition to a semiconductor element such as a TFT which functions as a pixel switching element, a photo-sensor element built in a pixel region and capable of receiving light to produce received light data. A liquid crystal panel of the type just described is disclosed, for example, in Japanese Patent Laid-Open No. 2006-127212 and Japanese Patent Laid-Open No. 2007-128497.
The liquid crystal panel described can implement a function as a user interface by utilizing the built-in photo-sensor element as a position sensor element. Therefore, the liquid crystal panel is called I/O touch panel.
In a liquid crystal panel of the type described, it is not necessary to dispose a separate touch panel of the resistance film type or the electrostatic capacity type on the front face of the liquid crystal panel. Accordingly, reduction in size and thickness of an apparatus can be implemented readily. Further, where a touch panel of the resistance film type or the electrostatic capacity type is used, since the touch panel sometimes decreases the amount of light to be transmitted through the liquid crystal panel in a pixel region or gives rise to interference of light, the quality of the display image is sometimes deteriorated. However, where a photo-sensor element is built as a position sensor element in a liquid crystal panel, occurrence of such a fault as just described can be prevented.
In the liquid crystal panel, visible rays reflected from a detection object body such as a finger of a user or a touch pen which contacts with the front face of the liquid crystal panel are received by a photo-sensor element built in as the position sensor element. Thereafter, the position at which the detection object body contacts is specified based on received light data obtained by the photo-sensor element built in as the position sensor element. Then, an operation corresponding to the specified position is carried out by the liquid crystal display apparatus itself or an electronic apparatus which includes the liquid crystal display apparatus.
Where the position of the detection object body is detected using the photo-sensor element built in as the position sensor element in such a manner as described above, the received light data obtained by the photo-sensor element sometimes includes much noise from an influence of visible rays included in external light. Further, where black display is carried out in a pixel region, it is difficult for the photo-sensor element provided on the TFT array substrate to receive visible rays. Therefore, it is sometimes difficult to accurately detect the position of the detection object body.
A display apparatus has been proposed which uses invisible rays such as infrared rays in place of visible rays in order to eliminate such a fault as described above. The display apparatus of the type is disclosed, for example, in Japanese Patent Laid-Open No. 2004-318819 or Japanese Patent Laid-Open No. 2005-275644.
In the display apparatus mentioned, invisible rays such as infrared rays emitted from a detection object body are received by a photo-sensor element built in as a position sensor element to acquire received light data. Then, the position of the detection object body is specified based on the acquired data.